The present invention relates to bottom trawl fishing, and more particularly to an apparatus for connecting the sweepline to the hanging chain of a bottom trawl while stopping lateral movement of the rollers along the sweepline to prevent tangling of the trawl net with the sweepline, and tearing of the trawl net.
In bottom trawl fishing, the trawl net is towed along the ocean bottom behind the trawler. The trawl net forms an envelope with a closed back and sides and an open front for catching the fish. Floats attached to the upper leading edge of the trawl net keep it a pre-determined distance above the bottom. The lower leading edge of the trawl is dragged, or preferably, rolls along the ocean floor. The typical sweepline includes large rubber rollers. The lower leading edge of the trawl net is connected by hanging chains to the sweepline, which in turn is attached to the trawler.
The sweepline net is attached to the trawler through a pair of main wires and a pair of ground cables. Trawl doors, also known as otter boards, are angled to the direction of travel so that seawater forces the trawl net open. One ground cable attaches each trawl board to a side of the trawl net. Thus, the leading edge of the trawl net takes a "U" shape.
The rollers which are located in the center portion of the "U", are subjected to small lateral forces along the sweepline. However, rollers on the legs of the "U", known as wing rollers, are subject to significant amounts of lateral force. To date, there has been no satisfactory method for connecting the sweepline to the hanging chain of the bottom trawl while resisting the substantial lateral forces exerted upon the rollers.
The best known connection in the prior art is the "shackle in" rig which utilizes a pair of free-spinning washers on either side of a conventional shackle which is connected to the sweepline chain. As pressure is exerted by the rollers laterally along the sweepline, the washers spin with the rollers. These washers tend to wear rather quickly, enlarging the center hole, and the washer slips over the shackle followed by the roller, resulting in tangling and tearing of the trawl net.
In order to slow the wearing process, the washers can be made from thick steel--up to 1/2 inch thick. These thick washers are called "rollers plates" and can cost up to $6.00 a piece.
Others have attempted to develop an improved method of connecting the sweepline to the hanging chain in the past. One such example in the prior art, is sold by the Westerbeke Fishing Gear Company and is called the Trawl Spacer. This apparatus consists of a "dumb-bell" shaped plastic spacer having a stainless steel band around the central, reduced section, and a shackle attached to the band for connecting to the hanging chain. It has been found, particularly when this apparatus is used on the wing of the sweepline, that the spacer turns with the rollers. The strong lateral forces exerted by the wing rollers on the spacer tend to twist and bind the stainless steel band, and the band clamps firmly to the spacer. The result is that a large portion of the sweepline will begin pulling hanging chains around it, and cause tangling with the trawl net. Sometimes the damage is so extensive that entire sections of net must be replaced.
Another method for connecting rollers to a trawl net is disclosed in U.S. Pat. No. 2,910,796 to Paulsen. In that patent, wooden rollers on the sweepline are provided with integral extensions and slip rings around the extensions. The slip rings are attached directly to a cable passing through the trawl net. In this manner, the rollers are supposed to remain connected to the trawl net when the sweepline cable breaks. One drawback to the '796 patent is that it requires the use of special rollers as opposed to the large rubber rollers currently used by many fishermen. Furthermore, particularly on the wind of the sweepline, friction from the rubbing of adjacent roller extensions, and wearing and twisting of the slip rings, tends to bind and inhibit rolling, causing tangling of the trawl net.
It is therefore a principal object of this invention to provide an apparatus for connecting a sweepline to the hanging chain of a bottom trawl while stopping lateral movement of rollers along the sweepline.
A further object is to provide a sweepline connection which prevents the loss of rollers in the event the sweepline chain breaks.
Another object is to provide a secure connection to the sweepline without interfering with free rotation of the rollers.
A still further object is to provide an apparatus which is useful on the wing as well as the center of the sweepline.
Yet a further object is to provide an apparatus which can be constructed relatively simply and economically, and can easily be attached to existing sweeplines using rubber rollers.
Other objects will in part be apparent and in part pointed out hereinafter.